Our 13 year old zu has had for a few years now a large fatty lump on her chest she has no discomfort from it and the vet says it is harmless.but it is now rubbing on the floor when she walks.Iwill be glad of any comments.

If it's to that point, it may be causing her discomfort soon, as the area will lose its fur and may get raw.

Talk to your vet. There are a lot of risks for pets that age with anesthesia, but most of them come through it okay. You may want to talk to them about getting it removed.